JEE PYQ: Communication System Question 31
Question 31 - 2019 (11 Jan 2019 Shift 2)
An amplitude modulated signal is plotted below (V(t) with max 10V, min 8V, carrier period 8 $\mu$s, modulation period 100 $\mu$s). Which one of the following best describes the above signal?
(1) $(9 + \sin(2.5\pi \times 10^3 t)) \sin(2\pi \times 10^4 t)$ V
(2) $(1 + 9\sin(2\pi \times 10^4 t)) \sin(2.5\pi \times 10^5 t)$ V
(3) $(9 + \sin(2\pi \times 10^4 t)) \sin(2.5\pi \times 10^5 t)$ V
(4) $(9 + \sin(4\pi \times 10^4 t)) \sin(5\pi \times 10^5 t)$ V
Show Answer
Answer: (3)
Solution
Amplitude varies as $9 \pm 1$. $T_1 = 100\ \mu$s (signal), $T_2 = 8\ \mu$s (carrier). Equation: $[9 \pm \sin(2\pi \times 10^4 t)] \sin(2.5\pi \times 10^5 t)$ V.
BETA
